1. Field of the Invention
The present invention relates generally to filtering devices. In particular, the present invention relates to a renewable spin-on type filter having a high strength plastic housing.
2. Discussion of Background
Spin-on, twist-on type filters are used in numerous liquid and pneumatic applications throughout the agricultural, transportation, commercial and industrial markets. The housing or can for most spin-on disposable filters are manufactured from malleable materials, such as aluminum, by a deep-draw forming process. This technique limits the structural capabilities of current spin-on and twist-on type disposable products to the production capabilities of the metal forming industry and to the molecular characteristics of a limited number of specific malleable metals. Prior art disposable filters use stamped steel or cast cover plates to secure the housing or can to a mounting and distribution head assembly. This plate typically has a threaded center hole and is spot-welded and/or crimp-sealed to a deep drawn can. The purpose of the cover plate is to provide a mounting section that contains sufficient strength to allow operation of the filter at the required pressure rating. These prior art techniques for sealing and connecting the can to the plate, plus the structural limits of thin gauge malleable metals, restrict the application and uses of prior art spin-on, twist-on disposable filters. Recently, new high pressure, high burst strength disposable filter housings with burst pressure ratings in the 1000 psi range have been developed for some narrowly defined markets and applications. However, even these newer, high-strength filters remain applicationally limited because of their continued use of deep-drawn metal cans.
The filter media used in the prior art are usually paper products that are flexible and flimsy. As a result of their flexible and flimsy characteristics, these filters often are not properly secured in place within the housing or can during the assembly of the filter. By some accounts, 50% of current commercially available oil filters are defective and thus do not perform up to specification. Also, prior art paper filters often develop rips or tears during use. For example, if there is a spike in the pressure of the fluid being filtered, paper filters will often develop a rip through which unfiltered fluid flows. Such rips generally increase in size as a result of the rush of fluid flow there through. Such defects are not visible and unknown to the machine operator and the use of the filter continued for its normal use period during which improperly filtered oil is re-circulated through the machine or engine. Serious damage to the machine or engine can result. Once these disposable filters have been severed, they can no longer serve their purpose and should be replaced.
When conventional filters reach the end of their useful life, the filter is removed from the vehicle or machine and the remaining filtrate, usually oil, is drained and a new filter is installed. Thereafter, the filter should be compacted and disposed of in accordance with industry practice. However, often the used filter is disposed of in a way that it is eventually placed in a land fill. The impact on the environment from the disposal of used filters and oil is devastating to the environment. The enormity of this problem is realized when the variety of industrial and consumer applications that employ disposable filters, as well as the frequency with which these filters are replaced, is considered. The impact on the environment can be appreciated when it is realized that there are currently about 180,000,000 vehicles in the United States for which it is recommend that the filter and oil be changed every 3,000 miles. About 400,000,000 oil filters are manufactured in the U.S. each year, of which less than 25% are properly recycled. The remaining, which retain some oil, are disposed of and this used oil enters the environment. Even properly drained oil filters can retain up to 8 ounces of used oil. It is estimated that the result of proper recycling would result in the recovery of more than 17,000,000 gallons of oil. If properly processed, this oil could be reused.
Therefore, there exists a need for a twist-on filter that is renewable which would support and encourage the recycling of used oil and reduce environmental liability.
If an oil filter is not serviced, it can become clogged and the flow of incoming oil will be impeded and eventually completely stop from passing through the filtering media. When the filter becomes blocked with contaminates, fluid flow is restricted and diminished and the differential pressure across the filter element increases. As the volume of the flow diminishes, parts of the machine or engine that normally receive lubrication will receive inadequate lubrication. The typical lubrication systems for an internal combustion engine pump oil from a sump through a loop, splashing oil over and around moving engine parts, such as the valves and piston rods. The oil filter is a component through which the oil flows in this oil flow loop. Thus, if the oil filter becomes clogged, the flow of oil is impeded and lubrication becomes inadequate. However, the damage to an engine or machine will be less if the circulation of the contaminated oil is continued rather than allowing the circulation of oil to be stopped. Thus, it is important that a bypass be provided to allow the circulation of oil to continue when it cannot pass through the filter media. Also, when an engine that is in a cold environment is started, the viscosity of the crankcase oil is very high and resists being forced through the filter media. It is important, in such situations, that provisions are available to allow the oil to bypass the filter for a period while its temperature increases and its viscosity decreases. For these reasons, oil filters should have a bypass system to protect the engine in the event of a clogged filter. Bypass valves for oil filters are known. However, they are complicated, expensive and are not an integral part of the filter. There is a need for a filter device that has a simple mechanical bypass that is an integral part of the filter device and cannot be disconnected or tampered with.
A typical automotive poppet type bypass valve has a very limited surface area against which the liquid that is at an elevated pressure must react to cause the bypass valve to open. This renders the valve unreliable for its intended purpose. Also, the typical automotive poppet type bypass valve utilizes a compression spring to urge the valve closed. Compression springs are very vulnerable to premature fatigue failure. The filter of this invention has an infinite life and, thus, if the filter of this invention is provided, a built-in bypass valve should also have an infinite life. Another shortfall of the typical automotive type poppet bypass valve of the type that relies on a compression spring to return the valve to its closed position is that it is unlikely that full closure will be attained. Coil type compression springs are rounded on both ends and cannot be properly guided. As a result, compression springs take the path of least resistance when they expand. Furthermore, coil type compression springs do not exert an equal pressure over the length of their expansion and, thus, do not provide a uniform pressure on the poppet valve.
Accordingly, there is a need for a simple bypass valve that is built into a renewable filter that has an infinite life cycle to match the life cycle of the renewable filter. There is also a need for a filter having a bypass valve that has a relatively large surface against which the liquid at elevated pressure reacts to increase the reliability of the valve. Still further, there is a need for a filter having a bypass valve that does not rely upon a coil type compression spring to close the valve. There is also a need for a renewable filter having an integral bypass valve that, when fully open, has the capacity to bypass the full volume of the normal oil flow.
According to its major aspects and briefly stated, the present invention is a renewable twist-on filter that is made from a sealed polymeric, unitary housing that has a filter media assembly securely bonded in place within the interior of the housing. After a use period that can be measured either in elapsed time or, for automotive uses, in miles traveled, the filter will be removed and replaced. The filter that has been removed will then be cleaned, after which it is put back into circulation for another use period. The filter housing is plastic welded together and, thus, would be destroyed if it is opened or tampered with. The filter is designed to last for an unlimited time and is designed to withstand pressures in excess of three times the normal operating pressure that it is expected to be exposed to. In one embodiment of the invention, a bypass valve is built into the interior of the housing to allow circulation of the fluid to continue in the event, for example, that the filter becomes contaminated or in the event of a cold start. The filter housing carries a metallic adapter having machined threads for securing the filter housing to an engine or machine. Adapters can have internal or external threads and be of various sizes and thread types. It is also contemplated that this adapter could be formed of plastic material.
The housing formed from a hollow polymeric container. In a preferred embodiment, there is a polymeric container member having an open top and a polymeric top member that are plastic welded together to thus provide a closed housing having an interior chamber. The filter media is fabricated from multiple layers of metal mesh material and, thus, is a rigid stable item which assures that, in the assembly process, it is properly located. During the assembly process, the filter media is bonded in place within the interior chamber and its position within the chamber is assured by plastic welding of the container member to the top member. The assembly procedure guarantees the initial proper location of the filter media assembly and the plastic welding assures that this location will be maintained. Thus, the top member is fused to the hollow polymeric container and this assembly now functions as a closed housing having an interior chamber within which is securely attached the filter media assembly. It should be noted that, although the preferred embodiment discloses a housing formed from a cup-shaped member that is closed by a disc-shaped top member, the top member need not be disc-shaped but rather could also be cup-shaped. It should also be noted that, although the hollow polymeric container or cup-shaped member is disclosed as being a unitary cast part, it could also be fabricated from a section of polymeric tube having a molded bottom end member bonded or welded thereto. The essential feature being that the components from which the hollow housing are formed are welded together to form a closed housing having an interior chamber within which is securely attached the filter media assembly. The filter media assembly is secured by adhesive at both ends within the housing such that the filter media assembly is immovable relative to the housing. The bottom of the filter media assembly is secured to the bottom or closed interior end of the housing by an adhesive material. The top of the filter media assembly is also bonded to a media collector plate that is connected to the inner surface of the top member. The filter media assembly divides the interior chamber of the housing into an inlet section and a discharge section. The filter media assembly could be any type that is commonly employed in the art provided it is capable of being cleaned and subsequently reused.
The preferred embodiment of the filter media assembly formed from three layers of metal mesh material. Each layer is cut to a shape having a pair of edges that, when joined by a weld or encapsulated by adhesive, cause the flat piece of material to assume the shape of a cone. The metal mesh material is folded or pleated radially such that, after the edges are joined, the filter is in the shape of a truncated cone having continuous top and bottom edges. The pleats extend from the top continuous edge to the bottom continuous edge. The surface area of the filter media assembly is greatly increased by such a filter design. The inner and outer metal mesh material layers are formed of relatively large stainless steel wire and have relatively large openings. These layers of metal mesh function mainly as supports and protection for the central layer which formed from much smaller wires and has very small filtering openings. An important function performed by the heavy gauge inner and outer layers is to assure that the pleats of the central layer do not collapse upon each other to form a double layer.
When the filter requires cleaning, it is removed from the distribution head of the vehicle or machine, and the excess fluid contained therein is drained out. This small amount of drained fluid can be easily disposed of in a manner that is not detrimental to the environment. Thereafter, the filter is back flushed using a cleaning solution. Once cleaned, the filter may be dried prior to reuse by allowing it to stand for a period of time or by blowing a drying gas therethrough. As a result of using the highly efficient and reliable filter, it is not necessary to change the oil each time the filter is cleaned. Test vehicles have currently exceeded 12,000 miles without an oil change and test of the oil shows little deterioration.
A major feature of the present invention is the unitary design of the polymeric housing.
Still another feature of the present invention is the combination of a polymeric housing and a renewable filter media assembly. This combination enables the filter to be cleaned and recycled which, in turn, significantly reduces the deleterious impact on the environment.
Another significant feature of this invention is the provision of a filter that has been provided having a bypass valve within the confines of the filter that requires no external conduits or accessories. This bypass valve, like the filter, has been designed for an infinite life cycle. The closure member for the bypass valve is maintained in a precise disposition as it is compressed as a result of it being guided by the outer surface of a brass adapter. This assures a full closure of the valve. Applicant""s stainless steel spring engages the closure member at a plurality of equally spaced locations to exert a force on the closure member causing it to slide smoothly without binding along the smooth outer annular surface of the threaded adapter. As a result applicant""s bypass valve will always return to its full closed position. The closure member of the bypass valve has a reaction surface area that is sufficient to insure that when fully open the bypass valve can bypassing the full volume of the normal oil flow. This is particularly important in cold start situations since it permits the full flow of unfiltered oil.